Radio transmitting apparatus



Nov. 4, 1930. w. M. BROWER 1,780,167

RADIOTRANSMITTING APPARATUS Filed March 20, 1928 INVENTOR Wl/(ium MBrewer A TTORNE YS Patented Nov. 4, 1930 UNITED. STATES PATENT OFFICE,

WILLIAM M. BROWER, OF PALO ALTO, CALIFORNIA, ASSIGNOR '10 FEDERAL GRAPHCOMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALI FORNIARADIO TRANSMITTING APPARATUS Application filed March 20, 1928., SerialNo.'263',010,

This invention relates to radio transmitting systems and has to do mostparticularlywith systems intended for operation at extremely high radiofrequencies. 7

The primary object of the invention is to obtain frequency stability.

It has been the practice heretofore in vacuum tube. radio transmittingsystems to utilize a so-called master oscillator of rela- 1o tivelysmall power output and associate this with the transmitting antennathrough the medium of a vacuum tube relay or power amplifier which isasymmetrically conductive and therefore capable to a large extent ofelectrically isolating the master oscillator.

from the antenna, thereby preventing the frequency of the oscillatorbeing unduly affected by variations of the antenna constants. Thispractice works out satisfactorily at ordinary frequencies and at fairlyhigh frequencies; but when working with extremely high frequencies, sayat wave lengths of the order of 5 to 100 meters and thereabouts, it isfound that the intermediate or power amplifiers do not provide adequateisolation from the master oscillator, and consequently 7 do not performas well in the matter of maintaining frequency stability as they do atthe lower radio frequencies.

The present invention comprehends utilization of a master oscillatorwhich is magnetically and electro-statically isolated from both thetransmitting antenna and the power amplifier or intermediary relay andis coupled to the input of the latter only through a radio linkage whichprovides a unidirectional coupling.

More specifically, the present invention contemplates the combinationwith a transmitting' antenna of a thermionic amplifier comprising one ormore stages of amplification, the input end of which is coupled to asmall receiving antenna which is arranged to pick up radio waves whichare propagated 5 from a master oscillator of relatively small 7 therelatively short wave-lengths, the. frequency of the master oscillatoris particularly sensitive to changes in the electrical characteristicsof its circuits. When such an oscillator is coupled to the'input of anelectron relay amplifier, it is difficult 'to maintain it ata constantfrequency, due in part to reaction of the amplifier'uponthe oscillator.Furthermore in such case various adjustments made upon the amplifierserve to affect the frequency of the oscillator. I

As outlined above, in accordance with my invention I couple the outputof the oscillator '11 to a localanten'na 12.

This antenna is preferably of relatively small dimensions so that eventho it receives energy continuously from the master oscillator, it willnot interfere with the transmission of modulated energy from the mainantenna to be presently described. Its small dimensions also prevent itfrom effecting undesired variations in the frequency ofthe oscillator. V

r The remainderof the transmitting apparatus comprises an electron relayamplifier 13 the output, circuit of which is coupled to the usual mainantennagl f. It is apparent that amplifier 13 may have one or moreamplifierstages, and. in this particular case I have illustrated anintermediate amplifier relay 16, and a-power amplifier relay 17.

The input toamplifier l6=is coupled to'a local antenna 18, simliar tothe local antenna 12.

Antenna 18 and the input of amplifier 16 are tuned to the frequency ofmaster oscillator 11, or to the frequency of the energy being radiatedby local antenna 12. Local antennae 12 and 18 are located sufiicientlyclose together that antenna 18 intercepts an appreciable amount ofenergy radiated from antenna 12, but not so close that capacitative orinductive coupling is provided. In other words in so far as inductive orcapaoitative coupling is concerned, master oscillator 11 is entirelyisolated. from the electron relay amplifler 13. I have found that theenergy picked up by the local antenna 18 is sulficient to excite theelectron relay amplifier, so that the output of this amplifier has sufmyhand.

WILLIAM M. BROVVER.

ficient power to supply the main antenna 14:. v

In order to avoid disturbing the adjustments-of the'masteroscillator 11,I prefer to effect modulation of transmitted energy by means associatedwith the remainder of the transmitting apparatus. For example Ihave-shown a key 19 inserted in the grid circuit of amplifying relay,16, whereby the signal energy may be modulated in accordance withtelegraph code combinations.- With apparatus constructed in accordancewith this invention, the master oscillator may be operated at shortwavelengths of between 5' to meters, and its frequency will remainsufliciently constant for all practical signaling purposes. Itsfrequency will not vary during operation of the remainder of theapparatus or when adjustments are being made in the amplifier 13 or themain antenna. I have found that with such apparatus I may dispense Withthe use of special frequency controlling devices such as quartz crystalsand the like.

The invention is not to be confused with systems in which signals arereceived from a remote point and relayed to another station. Myinvention is designed to primarily solve the problem of keeping thefrequency of a master oscillator relatively constant, and the oscillatorin this case is located at the same station as the main transmittingequipment. Furthermore in my apparatus the high frequency energyreceived by the local antenna-18 is not integrated or detected beforebeing amplified and impressed upon the main antenna 14'. i

*I claim:

A radio station transmitting equipment comprising a main antenna,electron relay amplifying means having output and input circuits, theoutput-circuit being coupled to said main antenna, said means serving toamplify oscillatory energy impressed upon its input circuit withoutintegration, arelativ'ely small local antenna coupled to said 7 inputcircuit,a' local master oscillator of the electron relay type andoperative to generate

